The goal of this project is to develop improved methods for the remediation and risk assessment of complex mixtures. To accomplish, the project consists of three separate, but closely linked components: (1) studies to monitor and model environmental exposures in three diverse areas; (2) studies to estimate bioavailability in vitro and in vivo using rodent and swine models; and , (3) a series of bench, pilot and field scale trials to develop remedial procedures for contaminated media. Exposure assessment studies will be conducted in Channelview and Hidalgo County, TX, as well as a more heavily contaminated area in Azerbaijan. A historic database of five years from Channelview will be used to evaluate existing exposure and risk assessment models to guide modifications necessary in sampling regimens and model equations. The Azerbaijan studies will be linked to population studies conducted in Project 7. A series of in vitro studies will be conducted to investigate the impact of soil parameters (i.e., soil texture, organic matter) on bioavailability. Based on these data as well as characterization and fractionation studies (Project 2), two complex mixtures will be selected for in vivo bioavailability studies. Rodent studies (to be conducted at USEPA NHEERL) will evaluate the impact of a range of parameters on contaminant uptake. More limited studies will be conducted using mixed breed swine as a model for childhood ingestion of soil. The final component of this project will be studies aimed at the remediation of complex mixtures. Studies will continue to investigate factors affecting natural attenuation at the San Jacinto Wetlands Research facility in Channelview. In addition, pilot and field scale trials will be conducted to investigate the utility of clay-based technologies developed in Project 5. Bioremediation studies will also be conducted using two field sites which have been monitored by our program for the last five years and additional sites selected by the USEPA Office of Solid Waste Bioremediation in the Field Program. The outcome of this research will be a cleared understanding of the controlling processes that can be used to reduce the uncertainty associated with exposure to complex mixtures, and to improve techniques for detoxification of these mixtures.